The geodynamics component of this project seeks to link deep Earth structure with surface geology and explore the general processes by which the deep Earth and surface co-evolve throughout the Wilson cycle. Flat slab subduction as inferred underneath Colombia is one of such mechanisms and has been linked to extensive volcanism and mountain building away from the plate boundary along the Cordillera of the Americas. In particular, we will use numerical models to study time-dependent subduction and how the vertical deformation at the surface responds for general oceanic-continental plate interactions, and the regional setting where the overriding plate has inherited zones of weakness from past deformation.
Preliminary geodynamic model for the surface and uppermost mantle effects of the transient slab-flattening scenario of Wagner et al., (2017). Surface plots show flow-induced (dynamic) topography (left) and change in topography relative to last time-step (middle and right). Middle and bottom rows show vertical (shading) and horizontal (vectors) mantle flow velocities and slab anomalies (red contours) at two different depths. The computations consider viscous, 3-D flow effects of slab segments under Colombia alone, for visualization purposes. Slab viscosity is ~1000 times the ambient mantle.
Self-consistent dynamic models of subduction rollback exploring overriding plate stress and topography during slab interaction with a viscosity increase at 660 km depth and a high viscosity keel, which leads to a flat slab scenario. Mid and bottom rows show velocities (~8cm/yr maximum speed) and cold slab contours on top of horizontal normal stress (compression negative) for models with (bottom) and without (top) a strong keel (green outlines) for three time steps (different columns). Top row shows the inferred dynamic topography for keel (blue) and no keel (green) cases. Methods as in Holt et al., (2015), also see Faccenna et al. (2017a).
